Experiment Study On The Railway Subgrade Reinforced By Concrete Rammed Cast-in-Situ Pile And Geocell

Subgrade defects are widespread in our country and with the increasing of axle weight and running speed the trend is deteriorating day by day. For the ill subgrade in use, concrete rammed cast-in-situ pile and concrete rammed cast-in-situ pile combined with geocell are swift and high-efficient methods, worth popularizing.Based on renovating the subgrade of dacheng-railway and chengtiebeihuan-railway, this experiment was carried out to analyse the practical effect. Three kinds of test sections were mainly divided: normal sections, sections reinforced by concrete rammed cast-in-situ pile, sections reinforced by concrete rammed cast-in-situ pile combined with geocell. In order to reflect the dynamic properties of subgrade, the experiment items mainly included longtime subsidence, dynamic stress, dynamic displacement, acceleration, dynamic velocity, etc.According to the leveling data, generally 4 months or so is needed for reinforced sections to steady; because the reinforced subgrade is disturbed deeply, at initial stages it subsides rapidly; after 10 months subsidence speed of reinforced sections is lower than 10mm/y. The subgrade" s dynamics data got in the experience are in rational range. Compare with vehicle, the locomotive, which producing dynamics indexes obviously great, becomes the decisive factor of the dynamic state of subgrade. Due to track irregularity, dynamic response of the reinforced subgrade is relatively great; but the dynamic deformation modulus Kd, subgrade coefficient K30, the bearing capacity of foundations [a] etc show that the schemes can improve subgrade" s strength, stiffness and bearing capacity, reaching the project demand.The results have demonstrated that the two schemes of concrete rammed cast-in-situ pile and concrete rammed cast-in-situ pile combined with geocell can improve subgrade's intensity and capability of resisting deformation, reaching an ideal reinforcement effect.